Internal combustion engines, such as a gasoline engine, produce a variety of waste gases that are expelled from the cylinders through the cylinder head during operation. Some of these gases may be expelled into the atmosphere while some may be recycled by the engine through the use of an exhaust gas recirculation (EGR) system. An EGR system can reduce nitrogen oxide (NOx) emissions to the atmosphere by allowing the engine to replace a portion of its intake gases with exhaust gases. Allowing the EGR system to control the ratio of these gases within the cylinders can effectively lower the temperatures of the cylinders by limiting the amount of combustible intake gas available during each combustion cycle. The reduction in cylinder temperatures provided by an EGR system simultaneously reduces NOx generation because NOx forms mainly within a narrow temperature range near peak cylinder temperatures. One problem that arises with such systems is that the gas from the EGR system is relatively hot compared to the intake gas. Hot exhaust gases routed back into the cylinder can lead to degradation of valves, less efficient combustion, and increased cylinder temperatures, thereby cancelling some of the benefits gained through the implementation of the EGR system.
One example of a solution to the problem of recycling hot exhaust gases is to integrate a cooler system within the EGR system. An EGR cooler helps to reduce the temperature of the recycled exhaust gases before they are released into the intake manifold (and in turn, the cylinders). EGR coolers are often comprised of a unit with a series of inlets and outlets for both input and output of EGR gases and coolant. The EGR cooler may be mounted to a surface within the engine compartment, in close proximity to the engine. EGR coolers may have a number of fittings used to couple with tubes and/or pipes for coolant and gas exchange.
However, the inventors herein have recognized potential issues with such systems. As one example, the fittings of an EGR cooler are often subjected to intense temperatures and involve extended contact with fluids. As a consequence, the materials used to construct fittings to fulfill these requirements are often exotic and/or expensive. In addition, the assembly and repair of the fittings can also be time-consuming and increase labors costs. EGR cooler fittings may develop leaks and because the coolers are often located near several high-temperature areas of the engine (such as the cylinder head and exhaust manifold) a leak in the fittings can result in engine degradation. The coolers and their connections also tend to be bulky and increase the overall volume occupied within the engine compartment.
In one example, the issues described above may be addressed by an exhaust gas recirculation (EGR) system, comprising: an EGR cooler module including a body and an EGR inlet port, EGR outlet port, and coolant inlet port, all extending from the body and arranged in parallel with one another and at a same, first side of a cylinder head, where the EGR inlet port and coolant inlet port are directly coupled to the first side of the cylinder head. In this way, the EGR cooler module may interface directly with coolant and gas passages within the cylinder head. In one example, the bolts that mount the EGR cooler module to the surface of the cylinder head also compress a gasket that seals the connection between the surfaces. The result is that the EGR cooler module has a compact form with fewer fittings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
FIG. 2 and FIGS. 4-6 are shown approximately to scale.